PGP and cancer: Among the many ABC transporters, subfamily members as P-glycoprotein (shorted as P-gp, encoded by ABCB1 gene), BCRP (referred to the breast cancer resistance protein, encoded by ABCG2 gene) and MRP1 (the multidrug resistance associated protein 1, encoded by ABCC1 gene) are the key triggers of MDR [1, 16].